Re: Use C99 designated initializers for some structs

From: Andres Freund <andres(at)anarazel(dot)de>
To: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Mark Dilger <hornschnorter(at)gmail(dot)com>, David Steele <david(at)pgmasters(dot)net>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Use C99 designated initializers for some structs
Date: 2018-08-30 20:14:31
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On 2018-08-30 13:54:41 -0300, Alvaro Herrera wrote:
> On 2018-Aug-30, Mark Dilger wrote:
> > static struct config_bool ConfigureNamesBool[] =
> > {
> > {
> > {"enable_seqscan", PGC_USERSET, QUERY_TUNING_METHOD,
> > gettext_noop("Enables the planner's use of sequential-scan plans."),
> > NULL
> > },
> > &enable_seqscan,
> > true,
> > },
> Personally, I dislike this form -- it's very opaque and I have to refer
> to the struct definition each time I want to add a new member, to make
> sure I'm assigning the right thing.

Dito. Especially because it looks different for the different types of

> I welcome designated initializers in this case even though it becomes
> more verbose. I don't think explicitly initializing to NULLs is
> sensible in this case; let's just omit those fields.

Yea - I mean a large portion of them previously weren't initialized
either, so there's really not a good reason to change that now.

> > What should the general rule be for initializing arrays of structs such as these?
> I don't know what a general rule would be. Maybe we can try hand-
> inspecting a few cases, and come up with a general rule once we acquire
> sufficient experience.

I think we should have as rules:

1) Members should be defined in the same order as in the struct, that's
the requirement C++ standard is going to impose. Think it's also
reasonable stylistically.
2) It's OK to omit setting members if zero-initialization obviously is

We probably should also check how well pgindent copes, and whether that
dictates some formatting choices.


Andres Freund

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